Ninchanese is a complete way to learn Chinese. Its online course allows you to learn and practice how to read, write, speak and understand Chinese in an enjoyable manner. It combines game mechanics... Read more.

ChineseMe is the most integrated Mandarin course, designed for motivated learners who have decided to become fluent. It is an interactive textbook that adapts itself to your interests. The course i... Read more.

Daily Chinese Sentence is an online and ongoing course that provides you every day with a unique Mandarin lesson straight to your inbox. You’re presented each time with a key sentence for which the... Read more.

A London-based school that takes their Mandarin courses to the next level - integrating technology (bespoke Phone Flashcards) and HSK test planning into their courses from Beginner, Intermediate to... Read more.

From their website (if you have personal experience of their courses, please leave a comment):
New Concept Mandarin specializes in teaching Mandarin Chinese (Putonghua) as a second language. Act... Read more.